This project has two objectives: A) To define the mechanism of impaired bile acid absorption in hypertriglyceridemia (specifically we will determine if the active or passive component of absorption is abnormal) and B) to determine the contribution of an alternative pathway of bile acid synthesis which begins with 27-hydroxylation of cholesterol. Because 27-hydroxylase is present in endothelial cells as well as liver, this pathway may play a role in removal of cholesterol from incipient atherosclerotic plaque.